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## Summary
This PR adds tests that verify that the magic trailing comma is not respected if disabled in the formatter options.
Our test setup now allows to create a `<fixture-name>.options.json` file that contains an array of configurations that should be tested.
<!-- What's the purpose of the change? What does it do, and why? -->
## Test Plan
It's all about tests :)
<!-- How was it tested? -->
## Motation
Previously,
```python
x = (
a1
.a2
# a
. # b
# c
a3
)
```
got formatted as
```python
x = a1.a2
# a
. # b
# c
a3
```
which is invalid syntax. This fixes that.
## Summary
This implements a basic form of attribute chaining
(<https://black.readthedocs.io/en/stable/the_black_code_style/current_style.html#call-chains>)
by checking if any inner attribute access contains an own line comment,
and if this is the case, adds parentheses around the outermost attribute
access while disabling parentheses for all inner attribute expressions.
We want to replace this with an implementation that uses recursion or a
stack while formatting instead of in `needs_parentheses` and also
includes calls rather sooner than later, but i'm fixing this now because
i'm uncomfortable with having known invalid syntax generation in the
formatter.
## Test Plan
I added new fixtures.
